The late-day "melt-up" that pushed the S&P 500 index .SPX out of bear-market territory might be construed as good news. But it brings back echoes of the "flash crash" that saw markets dive by several hundred points in a matter of minutes, and it's a big reason many are staying away from the market.

"Everyone is scared in both ways -- the shorts are scared, the longs are scared, everyone is scared. The high-net-worth investor is very, very scared," said Stephen Solaka, managing partner at Belmont Capital Group in Los Angeles, which manages money for independent wealth advisers and family offices.